1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter�45.�Samba Performance Tuning</title><link rel="stylesheet" href="../samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.74.0"><link rel="home" href="index.html" title="The Official Samba 3.5.x HOWTO and Reference Guide"><link rel="up" href="Appendix.html" title="Part�VI.�Reference Section"><link rel="prev" href="Other-Clients.html" title="Chapter�44.�Samba and Other CIFS Clients"><link rel="next" href="ch-ldap-tls.html" title="Chapter�46.�LDAP and Transport Layer Security"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter�45.�Samba Performance Tuning</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="Other-Clients.html">Prev</a>�</td><th width="60%" align="center">Part�VI.�Reference Section</th><td width="20%" align="right">�<a accesskey="n" href="ch-ldap-tls.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="speed"></a>Chapter�45.�Samba Performance Tuning</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Paul</span> <span class="orgname">Dundee Limb Fitting Centre</span> <span class="surname">Cochrane</span></h3><div class="affiliation"><span class="orgname">Dundee Limb Fitting Centre<br></span><div class="address"><p><code class="email"><<a class="email" href="mailto:paulc@dth.scot.nhs.uk">paulc@dth.scot.nhs.uk</a>></code></p></div></div></div></div><div><div class="author"><h3 class="author"><span class="firstname">Jelmer</span> <span class="othername">R.</span> <span class="orgname">The Samba Team</span> <span class="surname">Vernooij</span></h3><div class="affiliation"><span class="orgname">The Samba Team<br></span><div class="address"><p><code class="email"><<a class="email" href="mailto:jelmer@samba.org">jelmer@samba.org</a>></code></p></div></div></div></div><div><div class="author"><h3 class="author"><span class="firstname">John</span> <span class="othername">H.</span> <span class="orgname">Samba Team</span> <span class="surname">Terpstra</span></h3><div class="affiliation"><span class="orgname">Samba Team<br></span><div class="address"><p><code class="email"><<a class="email" href="mailto:jht@samba.org">jht@samba.org</a>></code></p></div></div></div></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="speed.html#id2690558">Comparisons</a></span></dt><dt><span class="sect1"><a href="speed.html#id2690596">Socket Options</a></span></dt><dt><span class="sect1"><a href="speed.html#id2690693">Read Size</a></span></dt><dt><span class="sect1"><a href="speed.html#id2690737">Max Xmit</a></span></dt><dt><span class="sect1"><a href="speed.html#id2690785">Log Level</a></span></dt><dt><span class="sect1"><a href="speed.html#id2690809">Read Raw</a></span></dt><dt><span class="sect1"><a href="speed.html#id2690876">Write Raw</a></span></dt><dt><span class="sect1"><a href="speed.html#id2690928">Slow Logins</a></span></dt><dt><span class="sect1"><a href="speed.html#id2690952">Client Tuning</a></span></dt><dt><span class="sect1"><a href="speed.html#id2690973">Samba Performance Problem Due to Changing Linux Kernel</a></span></dt><dt><span class="sect1"><a href="speed.html#id2691064">Corrupt tdb Files</a></span></dt><dt><span class="sect1"><a href="speed.html#id2691160">Samba Performance is Very Slow</a></span></dt></dl></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2690558"></a>Comparisons</h2></div></div></div><p> 2The Samba server uses TCP to talk to the client, so if you are 3trying to see if it performs well, you should really compare it to 4programs that use the same protocol. The most readily available 5programs for file transfer that use TCP are ftp or another TCP-based 6SMB server. 7</p><p> 8If you want to test against something like an NT or Windows for Workgroups server, then 9you will have to disable all but TCP on either the client or 10server. Otherwise, you may well be using a totally different protocol 11(such as NetBEUI) and comparisons may not be valid. 12</p><p> 13Generally, you should find that Samba performs similarly to ftp at raw 14transfer speed. It should perform quite a bit faster than NFS, 15although this depends on your system. 16</p><p> 17Several people have done comparisons between Samba and Novell, NFS, or 18Windows NT. In some cases Samba performed the best, in others the worst. I 19suspect the biggest factor is not Samba versus some other system, but the 20hardware and drivers used on the various systems. Given similar 21hardware, Samba should certainly be competitive in speed with other 22systems. 23</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2690596"></a>Socket Options</h2></div></div></div><p> 24There are a number of socket options that can greatly affect the 25performance of a TCP-based server like Samba. 26</p><p> 27The socket options that Samba uses are settable both on the command 28line with the <code class="option">-O</code> option and in the <code class="filename">smb.conf</code> file. 29</p><p> 30The <a class="link" href="smb.conf.5.html#SOCKETOPTIONS" target="_top">socket options</a> section of the <code class="filename">smb.conf</code> manual page describes how 31to set these and gives recommendations. 32</p><p> 33Getting the socket options correct can make a big difference to your 34performance, but getting them wrong can degrade it by just as 35much. The correct settings are very dependent on your local network. 36</p><p> 37The socket option TCP_NODELAY is the one that seems to make the biggest single difference 38for most networks. Many people report that adding 39<a class="link" href="smb.conf.5.html#SOCKETOPTIONS" target="_top">socket options = TCP_NODELAY</a> 40doubles the read performance of a Samba drive. The best explanation I have seen for 41this is that the Microsoft TCP/IP stack is slow in sending TCP ACKs. 42</p><p> 43There have been reports that setting <em class="parameter"><code>socket options = SO_RCVBUF=8192</code></em> in smb.conf 44can seriously degrade Samba performance on the loopback adaptor (IP Address 127.0.0.1). It is strongly 45recommended that before specifying any settings for <em class="parameter"><code>socket options</code></em>, the effect 46first be quantitatively measured on the server being configured. 47</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2690693"></a>Read Size</h2></div></div></div><p> 48The option <a class="link" href="smb.conf.5.html#READSIZE" target="_top">read size</a> affects the overlap of disk 49reads/writes with network reads/writes. If the amount of data being 50transferred in several of the SMB commands (currently SMBwrite, SMBwriteX, and 51SMBreadbraw) is larger than this value, then the server begins writing 52the data before it has received the whole packet from the network, or 53in the case of SMBreadbraw, it begins writing to the network before 54all the data has been read from disk. 55</p><p> 56This overlapping works best when the speeds of disk and network access 57are similar, having little effect when the speed of one is much 58greater than the other. 59</p><p> 60The default value is 16384, but little experimentation has been 61done as yet to determine the optimal value, and it is likely that the best 62value will vary greatly between systems anyway. A value over 65536 is 63pointless and will cause you to allocate memory unnecessarily. 64</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2690737"></a>Max Xmit</h2></div></div></div><p> 65 At startup the client and server negotiate a <em class="parameter"><code>maximum transmit</code></em> size, 66which limits the size of nearly all SMB commands. You can set the 67maximum size that Samba will negotiate using the <a class="link" href="smb.conf.5.html#MAXXMIT" target="_top">max xmit</a> option 68in <code class="filename">smb.conf</code>. Note that this is the maximum size of SMB requests that 69Samba will accept, but not the maximum size that the client will accept. 70The client maximum receive size is sent to Samba by the client, and Samba 71honors this limit. 72</p><p> 73It defaults to 65536 bytes (the maximum), but it is possible that some 74clients may perform better with a smaller transmit unit. Trying values 75of less than 2048 is likely to cause severe problems. 76In most cases the default is the best option. 77</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2690785"></a>Log Level</h2></div></div></div><p> 78If you set the log level (also known as <a class="link" href="smb.conf.5.html#DEBUGLEVEL" target="_top">debug level</a>) higher than 2, 79then you may suffer a large drop in performance. This is because the 80server flushes the log file after each operation, which can be quite 81expensive. 82</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2690809"></a>Read Raw</h2></div></div></div><p> 83The <a class="link" href="smb.conf.5.html#READRAW" target="_top">read raw</a> operation is designed to be an optimized, low-latency 84file read operation. A server may choose to not support it, 85however, and Samba makes support for <a class="link" href="smb.conf.5.html#READRAW" target="_top">read raw</a> optional, with it 86being enabled by default. 87</p><p> 88In some cases clients do not handle <a class="link" href="smb.conf.5.html#READRAW" target="_top">read raw</a> very well and actually 89get lower performance using it than they get using the conventional 90read operations, so you might like to try <a class="link" href="smb.conf.5.html#READRAW" target="_top">read raw = no</a> and see what happens on your 91network. It might lower, raise, or not affect your performance. Only 92testing can really tell. 93</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2690876"></a>Write Raw</h2></div></div></div><p> 94The <a class="link" href="smb.conf.5.html#WRITERAW" target="_top">write raw</a> operation is designed to be an optimized, low-latency 95file write operation. A server may choose to not support it, however, and Samba makes support for 96<a class="link" href="smb.conf.5.html#WRITERAW" target="_top">write raw</a> optional, with it being enabled by default. 97</p><p> 98Some machines may find <a class="link" href="smb.conf.5.html#WRITERAW" target="_top">write raw</a> slower than normal write, in which 99case you may wish to change this option. 100</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2690928"></a>Slow Logins</h2></div></div></div><p> 101Slow logins are almost always due to the password checking time. Using 102the lowest practical <a class="link" href="smb.conf.5.html#PASSWORDLEVEL" target="_top">password level</a> will improve things. 103</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2690952"></a>Client Tuning</h2></div></div></div><p> 104Often a speed problem can be traced to the client. The client (for 105example Windows for Workgroups) can often be tuned for better TCP 106performance. Check the sections on the various clients in 107<a class="link" href="Other-Clients.html" title="Chapter�44.�Samba and Other CIFS Clients">Samba and Other CIFS Clients</a>. 108</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2690973"></a>Samba Performance Problem Due to Changing Linux Kernel</h2></div></div></div><p> 109A user wrote the following to the mailing list: 110</p><div class="blockquote"><blockquote class="blockquote"><p> 111<a class="indexterm" name="id2690988"></a> 112<a class="indexterm" name="id2690994"></a> 113I am running Gentoo on my server and Samba 2.2.8a. Recently I changed kernel versions from 114<code class="filename">linux-2.4.19-gentoo-r10</code> to <code class="filename">linux-2.4.20-wolk4.0s</code>. Now I have a 115performance issue with Samba. Many of you will probably say, “<span class="quote">Move to vanilla sources!</span>” Well, I 116tried that and it didn't work. I have a 100MB LAN and two computers (Linux and Windows 2000). The Linux server 117shares directories with DivX files, the client (Windows 2000) plays them via LAN. Before, when I was running 118the 2.4.19 kernel, everything was fine, but now movies freeze and stop. I tried moving files between the 119server and Windows, and it is terribly slow. 120</p></blockquote></div><p> 121The answer he was given is: 122</p><div class="blockquote"><blockquote class="blockquote"><p> 123<a class="indexterm" name="id2691036"></a> 124<a class="indexterm" name="id2691043"></a> 125<a class="indexterm" name="id2691050"></a> 126Grab the mii-tool and check the duplex settings on the NIC. My guess is that it is a link layer issue, not an 127application layer problem. Also run ifconfig and verify that the framing error, collisions, and so on, look 128normal for ethernet. 129</p></blockquote></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2691064"></a>Corrupt tdb Files</h2></div></div></div><p> 130<a class="indexterm" name="id2691072"></a> 131<a class="indexterm" name="id2691079"></a> 132<a class="indexterm" name="id2691086"></a> 133Our Samba PDC server has been hosting three TB of data to our 500+ users [Windows NT/XP] for the last three 134years using Samba without a problem. Today all shares went very slow. Also, the main smbd kept spawning new 135processes, so we had 1600+ running SMDB's (normally we average 250). It crashed the SUN E3500 cluster twice. 136After a lot of searching, I decided to <code class="literal">rm /var/locks/*.tdb</code>. Happy again. 137</p><p> 138<span class="emphasis"><em>Question:</em></span> Is there any method of keeping the *.tdb files in top condition, or 139how can I detect early corruption? 140</p><p> 141<a class="indexterm" name="id2691117"></a> 142<a class="indexterm" name="id2691124"></a> 143<span class="emphasis"><em>Answer:</em></span> Yes, run <code class="literal">tdbbackup</code> each time after stopping nmbd and before starting nmbd. 144</p><p> 145<span class="emphasis"><em>Question:</em></span> What I also would like to mention is that the service latency seems 146a lot lower than before the locks cleanup. Any ideas on keeping it top notch? 147</p><p> 148<span class="emphasis"><em>Answer:</em></span> Yes. Same answer as for previous question! 149</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2691160"></a>Samba Performance is Very Slow</h2></div></div></div><p> 150<a class="indexterm" name="id2691168"></a> 151A site reported experiencing very baffling symptoms with MYOB Premier opening and 152accessing its data files. Some operations on the file would take between 40 and 15345 seconds. 154</p><p> 155<a class="indexterm" name="id2691181"></a> 156<a class="indexterm" name="id2691188"></a> 157It turned out that the printer monitor program running on the Windows 158clients was causing the problems. From the logs, we saw activity coming 159through with pauses of about 1 second. 160</p><p> 161<a class="indexterm" name="id2691201"></a> 162<a class="indexterm" name="id2691208"></a> 163Stopping the monitor software resulted in the networks access at normal 164(quick) speed. Restarting the program caused the speed to slow down 165again. The printer was a Canon LBP-810 and the relevant task was 166something like CAPON (not sure on spelling). The monitor software 167displayed a "printing now" dialog on the client during printing. 168</p><p> 169We discovered this by starting with a clean install of Windows and 170trying the application at every step of the installation of other software 171process (we had to do this many times). 172</p><p> 173Moral of the story: Check everything (other software included)! 174</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="Other-Clients.html">Prev</a>�</td><td width="20%" align="center"><a accesskey="u" href="Appendix.html">Up</a></td><td width="40%" align="right">�<a accesskey="n" href="ch-ldap-tls.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter�44.�Samba and Other CIFS Clients�</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">�Chapter�46.�LDAP and Transport Layer Security</td></tr></table></div></body></html> 175